After experiencing as much success as Sir Alex Ferguson did at Man United, you would be forgiven for assuming he didn't have too many regrets about his 27-year tenure.

But you'd be wrong. The Scot recently revealed that even on one of his best nights as Red Devils boss, he regretted one of his selection decisions.

Park Ji-Sung, who had played a crucial role in United's run to the Champions League final in 2008, was left out of the matchday squad to take on Chelsea in Moscow.

“It was a really great bunch of players with a great attitude about them and a good, strong squad,” Ferguson said.

“My problem in the 2008 final, maybe I even regret it to this day, was I left Ji-sung Park out completely in the final.

“He’d played such a great role and that’s the problem when you get to these finals."

That just shows how highly Ferguson regarded his South Korean talisman.

Park was Ferguson's go-to-guy in all of the big matches. He could have been out of the team for five games but the United boss always knew exactly what he was getting from him if a clash against Arsenal rolled around.

Even if there were players who were in better form or more technically gifted, Man Utd's legendary manager almost always picked Park on the important occasion.

And the 36-year-old has now revealed exactly what it was that convinced Fergie to select him.

In an interview on United's official website, Park admitted it was his high energy and defensive work that often gave him the edge.

"Maybe one of my strengths was to bring the energy to the team and then defensively I contributed a lot, compared to other players, which is quite essential for the big matches; you know, against big clubs you need to be very cautious with opponents that attack," the ex-winger claimed.

"So, with those kind of things, I could give some kind of trust to him [Ferguson] to perform well against big clubs. And then I really enjoyed playing against the big teams as well; the tension, the atmosphere and that kind of got me excited to deal with that.

"But I’m really pleased to have played a lot of big games and that allowed a good performance."

During Park's seven seasons at Old Trafford, he made over 200 appearances for the Red Devils, scoring 28 goals and becoming a firm fan favourite.

His status amongst the supporters was certainly boosted by his fondness for playing against Arsenal too.

He managed to find the back of the net of three occasions when taking on Arsene Wenger's team, including a memorable goal in the Champions League semi-finals in 2009.

And Park has admitted he enjoyed playing the Gunners because of the way they would usually set up against United.

He added: "I don’t know why I performed well against Arsenal but probably we prepared well and it could be their football style as well.

"They liked the passing game and then with me, we could take the ball and break down the game."

"That kind of football style could have been suited to me more, so that’s one of the reasons I performed well against Arsenal. It’s quite difficult to explain but I really enjoyed playing against Arsenal and I’m really pleased that we had great results against them during my career."